536 OF SENSATION. 



where such individuals have fallen under the care of judicious and per- 

 severing instructors, that their mental powers have been called into 

 their due activity, or that any ideas have been awakened, beyond those 

 immediately connected with the gratification of the animal wants, or 

 with painful or pleasurable sensations. Thus a mind, quite capable of 

 being aroused to activity and enjoyment, may remain in a condition 

 nearly allied to that of idiocy, simply for want of the sensations requi- 

 site to produce ideas of a higher and more abstract character than those 

 derived through the senses of Touch, Taste, and Smell. 



942. For the exercise of the sense of Temperature, the integrity of 

 the sensory apparatus contained in the Skin appears to be requisite ; 

 for it has been ascertained by the recent experiments of Prof. Weber, 

 that if the integuments 'be removed, the* application of hot 'or cold 

 bodies only causes pain, their elevation or depression of temperature 

 not being perceived ; and the same is the case when hot or cold bodies 

 are applied to the nerve-trunks. It is worthy of note that there are 

 many cases on record, in which the sense of Temperature has been lost, 

 while the ordinary Tactile sense remained ; and the former is sometimes 

 preserved, when there is a complete loss of every other kind of sensi- 

 bility. So again we find that the subjective sensations of temperature 

 (that is, sensations which originate from changes in the body itself, not 

 from external impressions) are frequently excited quite independently 

 of the tactual sensations ; a person being sensible of heat or of chilliness 

 in some part of his body, without any real alteration of its temperature, 

 and without any corresponding affection gf the tactual sensations. It 

 is curious that the intensity of the sensation of temperature should 

 depend, not merely upon the relative degree of heat to which the part 

 is exposed ( 933),' but also upon the extend of the surface over which it 

 is applied ; a weaker impression made on a larger surface seeming more 

 powerful -than a stronger impression made on a small surface. Thus, 

 if the forefinger of one hand be immersed in water at 104, and the 

 whole of the other hand be plunged in water at 102, the cooler water 

 will be thought the warmer ; whence the well-known fact that water in 

 which a finger can be held without discomfort, will produce a scalding 

 sensation when the entire hand is immersed in it. 



3. Of the Sense of Taste. 



943. The sense of Taste, like that of Touch, is excited by the direct 

 contact of particular substances with certain parts of the body : but it 

 is of a much more refined nature than touch, inasmuch as it communi- 

 cates to us a knowledge of properties which that sense would not reveal 

 to us. All substances, however, do not make an impression on the 

 organ of Taste. Some have a strong savour, others a slight one, and 

 others are altogether insipid. The cause of these differences is not 

 altogether understood ; but it may be remarked that, in general, bodies 

 which cannot be dissolved in water, alcohol, &c., and which thus cannot 

 be presented to the gustative papillae in a state of solution, have no 

 taste. This sense has for its chief purpose to direct animals in their 

 choice of food ; hence its organ is always placed at the entrance to the 



